DESCRIPTION: The objective of our proposal is to characterize the window of opportunity for CD8-induced killing of cells infected but not yet producing SIV in rhesus macaques (RM). To this end we will compare treatment of SIV infection in control animals and CD8-depleted animals. Although similar experiments were done before (in part) by us and others, those used RTI therapy (PMPA and FTC). Here, we propose that using an integrase strand transfer inhibitor (raltegravir - RAL), we will obtain qualitatively and quantitatively different results that will alow probing of the strength of the immune response during cell infection but before viral production (i.e., before integration). We will extend the standard and successful models of viral therapy to analyze the case of RAL monotherapy, because we expect that the behavior of the decay of virus is different. Analyzing viral load under RAL therapy (and its suspension) in CD8 depleted macaques will provide the best conditions to probe the effect of CD8s on controlling the virus. In addition, we will analyze the number of infected cells, with different forms of HIV DNA (integrated, unintegrated, 2LTR circles) to gain precious insights into the long-term dynamics of viral reservoirs, especially latently infected cells. Our specific aims are: Aim 1. Quantify the dynamics of SIV during RAL monotherapy in rhesus macaques (RM). Hypothesis: The profile of viral load under RAL monotherapy is due to decay of cells infected by virus that have not completed integration but which leak through and become productively infected. We will develop new models of viral dynamics, which take into account the specific mode of action of RAL. Thus, we will quantify the kinetics of cellular reservoirs with unintegrated HIV DNA. Aim 2. Quantify the effect of CD8+ T-cells in killing cells infected with SIVmac before they become productively infected (i.e., before proviral integration). Hypothesis: Most of the CD8+ T cell effect on killing infected cells occurs before the start of viral production by the infected cell. We will quantify te effect of CD8 on killing of cells with unintegrated DNA. Aim 3. Quantify and model the fate of different cellular/viral reservoirs during long-term SIV treatment. Hypothesis: Modeling of long-term combination therapy including structured RAL treatment interruptions will permit a characterization of the decay and maintenance of different cellular/viral reservoirs. We will measure cells with integrated and unintegrated viral DNA (eg., 2-LTR circles), latently infected cells and follicular dendritic cell-associated viruses. We will develop models of these cellular compartments to quantify their decay and understand whether they are replenished throughout treatment or if they continuously decrease. These studies will better characterize the strength of CD8+ T-cells in controlling infection and the long-term decay of different viral reservoirs. Thus, our results will have implications to HIV control (by vaccines and therapy) and probe the limits of the immune response in eradicating the virus.